Add infinite scroll in search results dropdown

Problem

When trying to invite a group that has more than 20 subgroups to a project, the "select a group" dropdown list only shows the first 20 items. This can lead to the desired group not being shown, and thus for the user being unable to select it.

Proposal

Add infinite scroll to the search results dropwdown to show all the groups that match the search. This should work for both the "Invite a group" feature on projects and groups.

Implementation plan

1. Switch app/assets/javascripts/invite_members/components/group_select.vue#L122 to GlListbox
2. Use Infinite scroll example as a guideline to implement